1. Field of the Invention
This invention relates generally to a corrosion inhibitor and, more particularly, to the use of certain acids as corrosion inhibitors in aqueous solutions, such as an antifreeze/coolant composition.
2. Description of Background Art
Automobile engine cooling systems contain a variety of metals, including copper, solder (especially high lead solder), brass, steel, cast iron, aluminum, magnesium, and their alloys. The possibility of corrosive attack on such metals is high, due to the presence of various ions, as well as the high temperatures, pressures, and flow rates found in such cooling systems. The presence of corrosion products within the cooling system can interfere with heat transfer from the engine combustion chambers, which may subsequently cause engine overheating and engine component failure due to excess metal temperatures. See generally Fay, R. H., "Antifreezes and Deicing Fluids", Kirk-Othmer Encyclopedia of Chemical Technology (1978) Vol. 3, pp. 79-95.
Furthermore, there is a growing desire to reduce the heavy metal contamination of spent engine coolant, in order to substantially eliminate the hazards of handling it, which is necessitated by environmental considerations aimed towards safe disposal.
U.S. Pat. No. 4,851,145 describes a corrosion-inhibited antifreeze/coolant composition, wherein the corrosion inhibitor includes a combination of (a) an alkylbenzoic acid or the alkali metal, ammonium or amine salt thereof, (b) a C.sub.8 to C.sub.12 aliphatic monobasic acid or the alkali metal, ammonium or amine salt thereof; and (c) a hydrocarbyl triazole.
U.S. Pat. No. 4,587,028 describes non-silicate antifreeze formulations which include a corrosion inhibitor including an alkali metal salt of benzoic acid, an alkali metal salt of a dicarboxylic acid and an alkali metal nitrate.
U.S. Pat. No. 4,584,119 describes an antifreeze composition including the dibasic salt of naphthalene dicarboxylic acid and, optionally, a triazole as a corrosion inhibitor.
U.S. Pat. No. 4,389,371 describes an antifreeze composition which includes a corrosion inhibitor having an effective amount of a conventional corrosion inhibitor selected from the group consisting of the alkali metal carbonates, borax, the alkali metal dichromates, the alkali metal silicates, phosphorus acid, phosphoric acid, an alkali metal tungstate, benzotriazole, tolyltriazole, an alkali metal salt of benzoic or toluic acid, an alkali metal salt of a phenol, an alkanolamine and an organo-silicone compound in addition to an alkanolamine phosphate and a heterocyclic nitrogen-containing compound.
U.S. Pat. Nos. 4,342,596 and 4,233,176 describe a non-petroleum based metal corrosion inhibitor prepared from aliphatic monobasic acids, certain aromatic acids, a lubricant, amines and water.
U.S. Pat. Nos. 4,241,016; 4,241,014; 4,241,013; and 4,241,012 describe hydroxybenzoic acid in antifreeze compositions as a corrosion inhibitor.
U.S. Pat. No. 3,425,954 describes a corrosion inhibitor including a mixture of an alkali metal salt of aromatic carboxylic acids (sodium benzoate), an alkali metal salt of nitrous acid (sodium nitrite), an alkyl ester of benzoic acid (butyl benzoate) and a stable compound having a triazole function (benzotriazole). The composition is incorporated in a carrier vehicle, such as propylene glycol, and is adapted to inhibit the corrosion of metals in the presence of hydrogen sulfide and carbon dioxide by direct contact or as a vapor phase inhibitor.
U.S. Pat. Nos. 4,501,667, 4,402,907, and 4,366,076 describe alkylbenzoic acids, such as 4-tert-butylbenzoic acid are useful as metal corrosion inhibitors.
U.S. Pat. No. 4,552,678 describes a corrosion inhibitor obtained from the reaction product of a polyamine, an anhydride, and an organic acid of the formula R.sub.2 -COOH where R.sub.2 may be H, a C.sub.1 to C.sub.12 alkyl, a C.sub.1 to C.sub.5 hydroxyalkyl, phenyl, tert-butyl, phenyl, or styryl radical.
U.S. Pat. No. 3,769,214 describes an aqueous lubricant composition containing a minor amount of a metal anti-staining agent and stability improver which is an alkanolamine salt of a carboxylic acid having at least 12 carbon atoms per molecule.
U.S. Pat. No. 2,832,742 describes the use of a blend of the diethanolamine salts of p-tert-butylbenzoic acid and a high molecular weight C.sub.7 to C.sub.18 aliphatic carboxylic acid mixture derived from an oxidized, petroleum fraction.
Japanese Patent No. 59208082 describes a method of inhibiting corrosion in a cooling water system for an internal combustion engine via addition of a corrosion inhibitor containing a water soluble amine salt of benzotriazole, a water soluble amine salt of t-butylbenzoic acid, a nitrite, and a benzoate to the cooling water.
U.K. Patent Application No. 2,122,598 describes a process and composition for resisting corrosion. The composition comprises (a) at least one C.sub.6 to C.sub.10 aliphatic carboxylic acid, (b) at least one C.sub.6 to C.sub.8 polyhydroxycarboxylic acid, and (c) at least one aromatic monocarboxylic acid, each of the acids being present as a salt with a salt-forming cation.
API Primary Petroleum Products Abstract No. 76-20709 describes French Patent No. 2268791, which discloses a water soluble ferrous metal corrosion inhibitor which is the condensation product of a C.sub.1 to C.sub.6 para-alkylbenzoic acid and an alkanolamine.
U.S. Pat. No. 4,497,702 describes amide reaction products of a polyalkylene polyamines and neo-acids. The reaction products are said to be useful to inhibit the corrosion of equipment in which petroleum or chemicals are produced or processed.
It is, therefore, my understanding that the use of the acids described herein as corrosion inhibitors in aqueous solutions, particularly antifreeze/coolant compositions, has heretofore been unknown; especially where the target substrate is high lead solder.